It is known to measure an electrical current without any potential via the magnetic field produced by it. Magnetic field sensors, e.g. Hall sensors, magneto-transistors or other semiconductor elements serve for determining the strength of the magnetic field, and these produce an output signal which is more or less proportional to the magnetic field. In order to avoid the influence of non-linearities and changes of the transfer factor of a magnetic field sensor, special circuit arrangements and methods able to be carried out by these have been applied.
EP 0 172 402 A1 for example discloses a circuit arrangement with which the fluctuations in the transfer factor of a magnetic field sensor may be compensated. For this one envisages superimposing a known auxiliary magnetic field on the magnetic field to be measured, wherein both fields are detected by the magnetic field sensor. At the output side of the magnetic field sensor the signal is supplied to a summing element in a manner such that the component of the auxiliary magnetic field may be filtered out. This signal component which may be traced to the auxiliary magnetic field is transferred to a correlator whose second input is a current generator voltage which provides the current producing the auxiliary magnetic field.
A regulator is arranged on the exit side of this correlator, which provides a control signal for the magnetic field sensor burdened with fluctuations which are compensated for in this manner.
At the same time it may be seen to be of a disadvantage that the accuracy and control speed of this conventional compensation circuit is limited. Furthermore the compensation circuit is built up at least partly of discrete, analog components which entails a corresponding installation expense with regard to space and manufacture.